1. Field of the Invention
The present invention relates to an antenna feed arrangement and, more particularly, to an antenna feed arrangement including a smooth-walled waveguide section at a first end of the feed arrangement, a corrugated waveguide section disposed at a second end of the feed arrangement which is designed to provide a zero reflection response at a first frequency of interest, and a quarter-wavelength transformer waveguide section disposed between the smooth-walled and corrugated waveguide sections which is designed to also provide a maximally flat response at a second frequency of interest to permit wide-band operation covering two widely separated frequencies of interest.
2. Description of the Prior Art
Corrugated feeds are usually characterized by a relatively large input reflection, which vanishes only at certain frequencies corresponding to the zeroes of the surface reactance due to the input corrugations. Various techniques have been devised to permit broadband operation of corrugated feeds.
One technique was disclosed in U.S. Pat. No. 4,021,814 issued to J. L. Kerr et al on May 3, 1977 where the corrugated feed included a ridge pattern with gaps therebetween in which the width of the gaps is greater than the width of the ridges.
Another technique was disclosed in U.S. Pat. No. 4,295,142 issued to H. Thiere on Oct. 13, 1981 where the horn includes a transition zone made up of a number of sections between a smooth-walled feed and a corrugated horn radiator. The corrugated section includes ring corrugations which have depths that become progressively less as they approach a subsection of regular corrugations and have apex angles which are greater than those of the regular corrugations.
A multifrequency antenna feed system is disclosed in U.S. Pat. No. 4,358,770 issued to T. Satoh et al on Nov. 9, 1982 which includes a corrugated horn and a diplexer to permit operation of two separate frequencies.
The problem remaining in the prior art is to provide a corrugated feedhorn which will operate over two widely separated frequency bands without the use of diplexers or other devices.